Which of the following is not correct ?

Question

(a) Ammonia is used as refrigerant

(b) A mixture of $Ca(CN)_2$ and $C$ is known as nitrolim

(c) A mixture of $Ca(H_2PO_4)_2$ and $C_aSO_4.2H_2O)$ is known as superphosphate of lime

(d) Hydrolysis of $NCl_3$ gives $NH_3$ and $HOCl$